School of Rock may be Andrew Lloyd Webber’s new West End musical, but the best song in it is not an Andrew Lloyd Webber composition.

The title song was written by Sammy James Jr, of the American garage rock band The Mooney Suzuki, and Mike White, who wrote the screenplay for School of Rock, the 2003 movie on which this show is based; he also played Ned Schneebly, “Satanic sex god” turned nerd, in the film.

If you’ve seen the movie you will recall the brilliant lines “Now can I please have the attention of the class … today’s assignment: kick some ass!” as Jack Black and his young protégés, The School of Rock, stormed their way through the Battle of the Bands contest with the eponymous number (also known as Zach’s Song).

The British version of the stage show, which opened tonight (Monday 14 November) at the New London Theatre, sticks to the movie as closely as groupies to a member of Van Halen. Julian Fellowes (yes, the Downton Abbey guy) wrote the book and the show contains few new elements, no novel “wow” moments, and rather too many average songs. Luckily, none of this really matters because the young actors who play the school kids are simply sensational.

There are 39 of them in the London production, working in three teams of 13 to comply with child working hour regulations, and they act, sing, dance, jump up and down a lot, and above all rock on their own instruments superbly. From the explosive power chords when “Zach” first picks up his guitar, you know you are in for something special. These British kids have to sound American, and do, and their energy, exuberance and sheer talent are exhilarating – and, unlike many child performers, they avoid the twin traps of precociousness and sentimentality. It’s a long way to the top if you wanna rock’n’roll, or so they say, but these young stars are already halfway there.

The Broadway version of School of Rock, starring Alex Brightman, opened last year.

The youngsters are so compelling that when the grownups are on stage you just want them to hurry up so the kids can come back on. This is a bit hard on David Fynn, who pretty much nails the Jack Black role of the loser, thrown out of his own band, who finds redemption in teaching the finer points of heavy metal to a class of 10-year-olds; in terms of expressing empathy with the pupils he is tutoring in the ways of rock, he’s perhaps even more convincing than Black. Florence Andrews is also good as the uptight head teacher searching for her inner Stevie Nicks, although it’s her trilling of an aria from The Magic Flute that wins her an encore.

Getting back to the new songs, composed by Lloyd Webber with lyrics by Glenn Slater, a couple – You’re in the Band and Stick It to the Man – work well but the rest are unmemorable, indeed slight, and the maudlin big ballad – Where Did the Rock Go? – sticks out like a foil-wrapped cucumber stuffed down a bass player’s thong. After School of Rock itself, the most effective number is In the End of Time (better known as Legend of the Rent), another (uncredited) survivor from the film, co-written by Black himself – “you’re not hardcore unless you live hardcore!”

Fellowes writes in the programme about his hitherto well hidden passion for rock’n’roll, apparently kindled as a four-year-old when his big brother brought home a copy of Bill Haley’s Rock Around the Clock. We also learn that the Lloyd Webber record collection includes works by AC/DC, Black Sabbath and psychedelic proto-metallers Vanilla Fudge, little evidence of which has ever found its way into his extensive back catalogue. You wouldn’t expect such pillars of the establishment to pay more than lip service to the message “rock is about sticking it to The Man”, and they don’t.

On the other hand, it’s impossible to compete with a film soundtrack that featured, among others, The Clash, Cream, Led Zeppelin, Jonathan Richman and The Modern Lovers, Ramones, and The Who. So it’s only sensible, perhaps, not to try. And to be fair to Lloyd Webber, he has backed up his proclaimed desire “to spread the power of rock as far and as wide as possible” by offering free licences to schools to perform the musical. Which will make a nice change from Joseph and the Amazing Technicolor Dreamcoat.

Journalist and author David Marsh, former lead singer with The Whatcha-Gonna-Do-About-Its, left the Guardian after 20 years in July 2016 to spend more time with his record collection. He presents a monthly show, The Beat Goes On, on Kennet Radio. David is the author of For Who the Bell Tolls: One Man's Quest for Grammatical Perfection.